Radio frequency circuit arrangement



' E. GREEN RADIO FREQUENCY CIRCUIT ARRANGEMENT 4r 4| 2 A Kl 3 K2 W k, 4

WI W2 %T *1 J J 1 1 awuamtoz E ERNEST GREEN M3 Wow j Patented Sept. 20,1932 Y ERNESTGREEN,OFLONDO N,-ENGIIAtI$iD,l"ASSiGNOR"1'0 mm emblemIc'laLA-LGQ -A ION oFDE AwARE,

ma anaemia,c eumlgmw mE ?a, Application nearebr'uajr 15, 1e2a-seri 11vo,

This invention relates "to circuit jarrange- V ments for use with highfrequencycurrents,

amplifier, inorder to and is partici'llarl-y applicableto amplifyingsystems dealing with very high ra-dio fre (g quencles. V I relatesto'amplifying'systems of the kind} in 5 More particularly the inventionwhich a Wheatstone bridge arrangement :is

employedlto decouple the input and-output circuits associated with a:thennionic :valve prevent: reaction at high frequencies. .Bridgearrangements of .;the kind are. described in the specification of. the

prior United :S'tates --application *Number 43,924,lfiled Julyi16,i1925.

The present' frequencies, and in :Whichsan improved; efliciency shallbeohtained without' undesirejd reaction between-the output :and'fi-nputcircuits. e V 1 capacitative reacta'n'ce, inductive lreactalnce andresistance" are equal .eachto each, while" predominantly inductivereactance at output frequencyv is provided in theleador' leads i tothegrid or grids ofethe valve-or valves, in

the, said bridge; the arrangement, being such, that alternatingpotential ofqoutput ireg quency 'is appliedytoi; the said grid or gridsand since the said bridge remains v balanced,"- no current of output,vfrequency is fed back tothe jinputtcircuitg V :In one way, of carryingoutitheiijnventiom the grid-anode space of an I amplifyingrthefre mionicvalve is placed in-;- one arm of permit the {flow of direct current-to"the 1 grid nvention has: for I its objects to providean amplifier of:the kind referred to, which shall serve as a frequency changer, Whichshall remain balanced over a rangeof beenobtain ll the of a the" valve;

1 the" opposite corner', '"'and the. inputcircuit-is metrically asrespects earth preventany tendency of late to earth as a whole. I

a4o;0g9, ane Gr at BritainfMai chj 192,3 E f a I neutral}point in the"input "circuit may b'e The elements in the arm of the inafte'r calledthe grid 'o fthe valve,

irequency betWeen the said 'grid and the cor .earthed through 1aresistance foralike pur-j grida'arin) containing the are adjusted so 'asto pro-= Vi'de an-inductive reactance'at the outp'utf presponding-diagonal. 'fpoint notv the "bridge; i;

. The gtrequired inductive "reactance inay, inf

some cases, be obtained by virtue. of the connection leads themselvesgizcin others'itiwill ibe necessary to adjust 1' the "variable induc tancein the grid armito obtain-the desired Value. Where the "connection?leadsdo notnecessary, thecondens'erlin the grid-arm ma ["beaom1tted at veryhlghi trequencies, how

inductanc e, e t v ance sundesiredmeaction. 7

g It,will,of-eoutee,beYapPreciatedthat themselves. provide sufficientinductance and F tithe use :of, thers'aid :variable inductancei'i'sever, it. will generally be fou -n d that the said 1-. connection leadsprovidemorethan sufficient-3; inductance, .inqvvhichtcase the,variablecon-" {denser is adjustedto compensatelzfor"excess;Therequiredin'ductancehaving r or ridarmg e remaining arms of the'bridgeare'then'adjusmdusothat capacitative freactance, induc I {tivejreactanceand resistance inall four armfs Wheatstone "bridge the other three armsof which comprise each a variablegcondenser, a-r 'variableresistance anda variable inductance in series. .The', arm .containing the gridanodespace of thevalve-a lso contains w 1; riable' resistance, ga-variableinductance and are equalfeach to'each. In thisfmanner' b'al i YisFmaintained over? a i range fof itrev.; f quenc'iesj,*-vvhile,--owingto the effective inan -X; ,tance in the grid circuit jot-the valve; andthei effect of? the outputi'current flowing facross f the bridge,certain voltage of the output ire i I enc'yaini. correctrphasef-is' applied-jr to the Thev output circuit which is Ltuned"to*a harmonic ofthe-input circuit')'-'" f is "connected 1i between L that comer?- or thebridge to Which the anode i connectediand' grld, Without; loss ofbalanceandiivvithout V i grid bias a strong drive shouldbe provided,in orderto-ensure that the output circuit shall be energized at the harmonicfrequency.

The above described circuit may be employed for all harmonics. If oddharmonicsonly are required, the circuit should be modified '(in a mannerknown per se) tojinclude a thermionicvalve' ineach of two opposite armsof th'ebridge;

themselvesto provide the whole or part of.

the desired resistance and reactance values a Preferably, however,variable-impedance decentre point ar,

vices are provided in thebridge for purposes of adjustment;

The inventi on invention;

Referring first toj Figure 1,,this lshows an Number 43,924, hereinbeforereferred to, and parts corresponding in, Figure 1 to parts cated'by likereference letters and numerals.

1 A, GfandFfare; respectivelyntheanode,

grid and filament'ofja valve. 7 Theconden'ser formedby A and Grisincluded in one of the arms of a Wheatsto'nebridge, the other'armsincluding condensers C1, C21 and, C3,':an'd

'pq 2. nd the grid circuit across 3and 4,; a

v h rimary. circuit comprises inductances 7 L1 and L2and'adjustablecondensers K1- and K2, the positive high tension powertween the inductances. I

supply being connected at the point beprimary and grid circuits Larefeach "consti tuted by two condensersinfs'eriesj'with the, he'd; his I,d i le .bu

not essential.

batteryshuntedbya condenser Z1;

It ,will be 'noted 'that 'as sofar described, the arrangement is:substantially identical is illustrated in the accom-zj pan'ying drawingof which Figs. land 2 shOW' in conventional diagrammatic 'form two.

, modifications. in accordance with the said;

small condenser n connected from the common point 3, of Gland C2 toearth, the primary circuit being connected across very high frequencies.

In applying the present invention to this arrangement, adjustableinductances P1, P2,

P3, P4 are inserted one in each arm of the bridge. 1 D]; is 7 anadjustable condensers inserted-in.thezgrid arm o'fsaid bridge, and M isachoke to supply the grid feed. S is a resistance. Y

' The i riput circuit R2 and the asso with that disclosed in Figure 1 ofUnited States application Number 43,924.

tances and {capacities .in thebridge arms are t adjusted to makethe-resistance, inductance and capacity mall the said arms equal to eachs other. fIn-othe'r w'ords,'ii:"rl, 1'2, 7'3, T4, are the" respectivetotal resistances of the,. -bridge -"arms, P1, P2, P3, P4Ethe respectivetotal inductances, and C1 C2, C3, the total capacities'qof three of. thearms, that of the grid arm being the'capacity D1 in series with thegrid-anode capacity of the valve, then ,the adjustment should besuchthat 1'1 r2;=13.=r'4 Pl-? P 2.=P3P= P-4; 01;

U2"=103 =the capaeityof the said grid arm.

I. D ,The adjustment isalsos'uchthtt in addition ShOWIllIl the saidPIIOIdIS ClOSUI'G aremdi-r.

tofulfilling thiS Tequirement, the parts P4 In'cas'es "where thefrequencies to be dealt are in question, thesep'arate inductances P1,

high frequencies with are low, a separate condenser D1 may I j V bedispensed with,-it beingpossible to obtain small ad ustableresistancesr1, r2, T3 and P2,-P3, P4 may be dispensed with, thenecessary inductive-values (which at .very high frequencies will beexceedingly small) being obstained by "suitably-arranging the variousconnecting leads and the adjustment to obtain theldesiredinductivereactance between the points 4 and G being obtained by means 10f I thecondenser D1,

,fFigur'e2shows s magma, in w en 'twovalves areprovided and which'issuit able for .the'production of odd I harmonies; *Theelectrodes of thesecond valve are designatedjby'ftheletters-AyG and F and,'asjwill-beseen, the grid-feed choke M, resistance," i S,- "and thecondenser Dl are duplicated for 7 Across th e circuit are tworesistances: the twoi'valves mam-e 5 f W1 aI1 d W2 in series, with-theircommon point connected through a blocking condenser ;Z to earth,:andtheinductance V of'the'grid circuitis coupled to the output circuit ofadrive oscillator ,(not shown), B is a bias Havingnow particularly"described and S2'and D1, D2.- i I As-"in the previous embodiment, thecone densers D1 and-D2 may be -dispensed'with I 1 atlowfrequencies"and'the -inductance coils 1, P2,-P3,;P4' maybe"dispensedwith at ascertained the nature of my said invention and. 'fwhatmanner'the "same 1s to be performed, I declare that what I claim is: '1. In anamplifying system, a thermionic valve, a circuit for impressing signaloscillations on the input elements thereof, an output circuit therefor,said first named circuit and said output circuit being uncoupledmagnetically, and means for applyingthe oscillations in said outputcircuit to the input elements of said valve, including means forpreventing exchange .of current between said circuits. 7

2. Invan amplifying system, a thermlonlc V valve, a circuit forimpressing signal oscillaof said tube, and means for applying the.

tions on the input elements thereof, an out put circuit therefor tunedto a harmonic of the frequencyof the impressed oscillations and meansfor applying'the oscillations in said output circuit to theinputelements of said valveincluding a balanced bridge circuit I adaptedto-preventa transfer of current between said circuits. r 5 3. In anamplifying system, a thermionic valve, a circuit for impressing signal.oscillations on the input elements thereof,- an output circuit tunedvtoa harmonic of said signal oscillations connected to the output elementsvoltage oscillations in said output circuit to the input elements ofsaid valve, including in-,

ductances reactive at harmonicfrequency for preventing energy transferbetweensaid circuits. L y a I 4. A Wheatstone bridge amplifying systemwhose output circuit is tuned to a harmonic 1 of the input circuitfrequency sa1d system comprising bridge arms whose capacitative quencyis applied to the said grid and since the said bridge remains balanced,no. current of output frequency is fed back to theinput circuit. V

5. An arrangement as claimed in claim 4,. in which variable inductancecoils are provid- 'ed in the bridge arms; I

6; An arrangement asclaimed in claim 4 in which avariable condenser isprovided in an arm of the bridge including the grid of,

avalve. a y

7. An arrangement as claimed 1n c1a1m 4 in which a choke coil'isprovided-in the grid feed circuit of the valve.

8. In short wave oscillation generators, a pair ofthermionic tubes inopposed relation,

said tubes each having anode,..cathode and I grid electrodes, an outputcircuit connected between the anodes of said tubes, a pair ofseriescapacities connected between the anode V of each of saidtubesan'dthe gridof the other of said tubes and means for-impressing oscils Ilations at signal frequency between the points of connectionvbetweensaid series capacities.

9. In a radiofrequency apparatus, a thermionicrelay having anode cathodeandgrid electrodes, a balanced bridge circuit each arm of which includesacapacity andonearm of which also includes the grid to. anode cap'acityof said relay, meansfor impressing oscillations at signa'l'frequencyacross a pair of conjugate nodal points on said bridge,.a 'tanl: circuitconnected across anotherfpair. of con ugate nodal points on said'bridgeand a harmonic of the signal frequency. I

means, to tunesaid last named circuit to 10. A thermlonlcj osclllationgenerator in- A:

cluding a thermionic tube having anode, cathode and grid electrodes, aWVheatstone bridge circuit having balanced arms, one of:

which includes the anode-togrid capacity of Y sa1d tube, means forimpressing voltage oscillations acrossthe input elementsof saidtube'including an. energized winding connected across a pair'of conjugatenodal points on said bridge, means for tuning said winding to 1 asignalfrequency, an output circuit connecte'd across another pair of conjugatenodal. po nts on said bridge circuit:one of said' points being, adjacentto 'theanode ofsaid tube, means for tuning the output, circuit to aharmonic of the input frequency, means ineluding capacity in one arm ofsaid bridge for lmpressi'ng voltage'oscillations at the harmonicfrequency from said output circuit to the input elements ofsaid tube,and means in one of said arms for preventing'current char acteristic ofthe output current from reach- 111g sa1d inputclrcuit including aninductance reactive at output frequency invone arm of said bridge.

11. In short wave oscillationgenerators, a opposed relation,

pair of thermionic tube's'in sa1d tubes'each having anode, cathode andgrid electrodes,

an output circuit connected of eachlof said tubes and the of said tubes,tions at signal of connection grid of the other harmonicvof the signalfrequency. 1

means for impressing oscilla- T frequency between the points 7 betweensaid series capacities, and means to-tune said output'circuit to abetween the anodes of said tubes, a pair of" series capacities connectedbetween the anode n R T c1a1m i

